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IS 14785 (2000): Automotive Vehicles - Determination of Road-load Constants by Coast Down Test Method [TED 4: Automotive Braking Systems]

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IS14785:2000

Indian Standard AUTOMOTIVE VEHICLES -- DETERMINATION OF ROAD-LOAD CONSTANTS BY COAST DOWN TEST METHOD

ICS 19.060; 43.020

0 B;S 2000

BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG NEW DELHI 110002

:May 2000 Price Group 3 Automotive Vehicle Testing and Performance Evaluation Sectional Committee, TED 8

FOREWORD

This Indian Standard was adopted by the Bureau of Indian Standards. after the draft finalized by-lhc Automotive Vehicle Testing and Performance Evaluation Sectional Committee had been approved by the Transport Engineering Division Council. The road-load constants of an automotive vehicle are needed for evaluation of the performance of an automotive vehicle such as fuel consumption, emission, etc, on a chassis dynamometer. Thcsc constants are used lo determine the ( load on the chassis dynamometer to simulate the power needed to propel the vchiclc at diffcrcnt speeds as per lhe appropriate driving cycle. This standard has beenprepared with a view to have a uniform procedure to be followed by the automobile manufacturers as well as the testing laboratories who. at present in the absence of this standard. have evolved their own practices for evaluating these constants.

The composition of the Committee rcsponsiblc for formulating this standard is given in Annex A

IS 14785 : 2000 Indian Standard AUTOMOTIVE VEHICLES -DETERMINATION OF ROAD-LOAD CONSTANTS BY COAST DOWN TEST METHOD

1 SCOPE 4 VEHICLE PREPARATION 1.1 This standard specifies the procedure for 4.1 The vehicle shall be clean and complete in all determining the equation of road-load resistance of respects, representative of production series. vehicle, including the aerodynamic and rolling 4.2 Vehicle shall be run-in as per manufacturer’s resistance by coast down technique. This data is recommendation. primarily intended for the road-load simulation on variable load curve chassis dynamometer. 4.3 The wheels of vehicle shall be free and without any parasitic drag. For vehicles with rear chain drive, This equation is expressed as F = u+6v2, where factors it shall be-ensured that there is no chain rubbing. a and b are the constants. 4.4 The weight of testing personnel riding the vehicle 1.2 However, it may be borne in mind that use of and instrumentation carried on the vehicle shall be each of these constants independently may not be part of vehicle weight ( see 8.2.1). Additional loads accurate. For example, the coefilcient ofrolling resistance may be addedto bring the actual weight during testing ‘a’ will not be accurate enough to use as a comparison to be within f 2 percent of specified weight. The of rolling resistance of tyre. distribution of weight among axles shall be as close 2 REFERENCES as possible to the values recommended by the mamiW~~ However, ifsumofmaximumrnded The following standards contain provisions which axle weights exceeds the gross vehicle weight, the through reference in this text, constitute provision of actual weight on the axle shall be in the same proportion this standard. At the time of publication, the editions of the ratios of the gross vehicle weight to the sum of indicated were valid. All standards are subject to maximum recommended axle weights. The actual load revision. and ~parties to agreements based on this condition and wheel reactions shall be recorded in standard are encouraged to investigate the possibility the report. of applying the most recent editions of the standards 4.5 Tyres which have covered only 10 ~percent or indicated below: less of their expected life shall befitted on the vehicle. IS No. Title The tread depth measurement method or tread wear indicators on the tyre may be used to assess tyre life. 9211: 1979 Denomination and definitions of At the start of the test, tyres shall be cold and shall weights of road vehicles be inflated to pressure specified for respective load 11422: 1986 Terms and definitions of weights of condition of the vehicle. two wheeled motor vehicles 4.6 The grade, quality, quantity of lubricants for various 3 DEFINITIONS moving parts, adjustments ofbrake, clutch, idling speed, etc, shall conform to the man-r ‘s recommendation. The vehicle may be serviced before the test wasper 3.1 LadenVehicle the procedure recommended by manufacturer. A vehicle loaded to the condition of weight required 5 FEATURES OF TEST TRACK for-establishing the road-load. The test shall be conducted on a dry, level test track NOTE - The load condition of the vehicle for which the road-load equation is to be determined, depends on with a coefficient of adhesion not less than 0.8, the end use of this equation. For example, for emission particularly in region where the test is to be conducted. measurement for statutory purposes, the load condition If test surface is of tar, it shall not be traffic smooth is the ‘Reference Mass’, whereas for design verification and surface shall not have become soft due to heat. tests, it may be the ‘Gross Vehicle Weight’. Longitudinal slope of the track shall-not exceed 3.2 Unladen Vehicle 0.5 percent and shall be constant within f 0.1 percent over the measuring strip. The track shall have sufbcient A vehicle in the condition of kerb weight as per the length and width for achieving the test speed and relevant Indian Standard, given in 2 above. carrying out the test safely. 1 IS 14785 : 2000

6 INSTRUMENTATION 8 COAST DOWN TEST

6.1 Fitment of instruments shall be as recommended 8.1 General by instrument manufacturer. All instruments and the 8.1.1 Coast down test for a specific test speed (v) is additional weights, if any, shall be mounted in such a basically to establish the road-load ‘F’ from the way that they do not affect the performance or stability deceleration by measuring time elapsed from speed of the vehicle and do not hamper rider/driver from ‘v + 6v’ to speed ‘v - Sv’, when the transmission is in normal driving of vehicle and carrying out tests. The neutral. From the values of ‘F at different speeds, instrument shall be positioned on the vehicle such values of constants ‘a’ and ‘b ’ in equation F = a + bv* that it does not significantly affect the aerodynamics are determined by best curve fit method. of the vehicle. 8.1.2 In the case of two wheelers, the recommended 6.2 Calibration of instrument shall be checked and height of rider shall be 1.7 f 0.05 m and the rider shall adjusted asper instrument manufacturer’s instructions wear helmet and proper riding gear. He shall be seated before commencement of test. upright on the seat provided for the rider, his feet upon the pedals or foot rests. This position shall, 6.3 Automatic speed and distance measuring nevertheless, allow the rider at all times to have proper instruments meeting following least count and accuracy control of the vehicle during the test. requirements shall be used. 8.1.3 While carrying out the test, the portion of the Parameter Least Count Accuracy test track where the vehicle is decelerated from ‘v + 6v’ to ‘v - 6~’ shall be kept approximately same in Speed O.lkmh O.lkm/h both directions to reduce the effect of track variation. This shall be followed for each test speed. Distance O.lm O.lm 8.1.4 Forimproving the consistency of the test results, Time 0.01 s 0.01 s it is preferable that : *’ 7 TEST REQUIREMENTS a) the test at all speeds is conducted by the same 7.1 The test shall be conducted when wind speed is rider/ driver. less than 3 m/s with~gusts less than 5 m/s. In addition, b) the test at each speed shall be done continuously the vector component across the test-road shall not without intermediate stoppage. be more than 2 m/s. The wind velocity measurement shall be done at a height of 0.7 m above the road 8.2 Testing Procedure surface. The ambient temperature shall be preferably 8.2.1 The test shall be conducted with the load condition between 15” to 40°C -and relative humidity shall given in 3.1. preferably be less than 75 percent. 8.2.2 Test Speeds NOTE -~ For proper consistency of test results, it is preferred that the tests are done with wind velocity less a) The test shall be conducted at least at 5 speeds. than 0.5 m/s. Difference between each test speed shall not be less than 10 km/h. 7.2 Air density when calculated as described below shall not differ by more than 7.5 percent from the b) The lowestspeed at which test is done shall not air density under reference condition: be less than 20 km/h.

c) However in case of vehicle with maximum speed attainable under the test load and track condition where is not exceeding 60 km/h, d, = air density at test site expressed in kg/m’, 1) the interval between test speeds (a) above (I, = airdensityatreference conditions = 1.168 kg/m), may be reduced to the extent particularly needed, but not less than 5 km/h P, = atmospheric pressure at test site kPa, P, = atmospheric pressure at reference conditions 2) the lowest speed (b) above may be reduced = lOOkPa, to 10 km/h. Tb = ambient temperature at test site K, and d) The highest speed shall be more than or equal T = ambient temperature at reference conditions. to speed at which road load equation is intended = 300K. to be used. However, the highest test speed shall 2 IS 14785 : 2000

not be more than 80 percent ofthe maximum 8.2.10 Repeat the tests ( 8.2.8 and 8.2.9 ) sufficient speed achievable by the vehicle under the test number of times to enable to select the lowest 10 load and test track condition. statistically consistent readings of IF,,,,,, at each speed. The reading shall be considered as statistically 8.2.3 The value of ‘6~’ shall not be less than 3 km/h consistent when the statistical error (P) calculated as and not more than 5 km/h. per formula given below is within 2 percent: 8.2.4 Mount the instrumentation on the vehicle and make necessary connections. p= k ” ’ loo = 24.24 F, p 8.2.5 During the test, the windows and other ventilating passages shall be kept closed. They may be kept open to the minimun extent needed for installing the where instruments. k=2,3forn= 10, s = standard deviation 8.2.6 The vehicle shall be warmed up by running the vehicle for at least 15 km, at test speed prior to test.

The test shall begin immediately after completion of F Inearl = average for force in both directions, and warming up. Warming up shall be repeated before F,v = average of 10 readings of ‘F,,,,:,‘. tests for each speed. NOTE - It may be necessary to select a different set of 8.2.7 The vehicle shall be driven along a straight line 10 readings if the condition given in 9.2 is not satisfEd. during the test. 8.2.11 Repeat the test for all the desired test speeds 8.2.8 Attain a speed of about 5 to 10 km/h above (see 8.2.2). Depending on consistent length of test (v + 6~) and shift the transmission of vehicle in neutral. track available, the tests may be carried out for more Measure time (t,) up to 2 decimal places required for than one speed in the same run. In such cases, as the the speed to reduce from ‘v + 6~’ to ‘v - 6~’ in one condition of 8.2.3 would not be satisfied, it shall be direction. In case the vehicle has transmission without ensured that the variation of the track does not affect manual control, the test shall be done by towing/ the test results. pushing the vehicle to achieve required speed and 9 CALCUIATION releasing the towing/pushing arrangement. In case of electric vehicles, if the regenerative braking system 9.1 The road load is calculated as : can be electrically switched off, disconnecting the F=a+bvZ drive from the wheels may be done by switching off the same and the power supply to the motor. If it is where not possible to do so, the motor should be decoupled F = road load, in Newton; before the test and the test shall be done by towing/ pushing the vehicle to achieve required speed and a and b = road load constants; and V = test speed, in km/h. releasing the towing/pushing arrangement. The towing/ pushing shall be done in such a way that it does not 9.2 Curve Fitting affect the test. 9.2.1 From the values of F, at atleast five test speeds, 8.2.9 Repeat the test immediately in the opposite the values of coefficients a and b shall bc calculated direction and note the time (t,) as explained in 8.2.8. using following formulae. The curve fitting error should Take arithmetic average (r) of t, and t2 from the value be within Z-percent. oft, calculate the deceleration force ( F,,) as:

a _ C Fw - bC v= ( b=nCvZ F-2:v2CF n nC v”-( c vy F = ~(Test load ). (6~ 1. (!I Newton mean 1.8. t Curve fitting error -

where 2-f (Few, -Fob)‘Fcwe ’ loo Test load = weight of test vehicle, in kg, as per 1’ n 3.1; I I fi = ( A factor to take into account the inertia of rotating parts), that is, 1 where for 2 and 3 wheelers and 1.035 for = number of test speeds, other vehicles; and = a + bvz, and ‘t’ = time, in seconds. Fob. = F, given in 8.2.10. 3 IS 14785 : 2000

NOTE - For finding values of a and b and error in curve 10.2 If the value of ‘a’ so obtained can be extrapolated fitting, standard software packages such as ‘Regression for loadconditions other thanthe test load, this can Analysis’ may be used. be done for loads up to + 10 percent of the test load 10 VALIDI’IYOF THE EQUATION with following correction:

10.1 The above road-load equation can be extrapolated Test Loaddenred up to speeds 20 percent -above the highest speed at a dcarrd = a tcded ’ which test has been conducted. Test Loadtc,ted

IS 14785 : 2000

ANNEX A ( Foreword)

COMMITTEE COMPOSITION Automotive khicle Testing and Petiormance Evaluation Sectional Committee, TED 8

Chairman SHRIR. RAMAKRISHNAN 28, I Cross Road Kasturi Bai Nagar Adyar, Chennai 600 020

Members Representing

SHRI R. R. G. MENON Ltd, Chennai SHRI R. C. BALAKRISHANAN( Alternate )

SHRI RAJAT NANDI Society of Indian Automobile Mamufacturers, New Delhi DR KOSHYCHERAIL (Alternate )

SHRI A. S. LAKARA Association of State Road Transport Undertakings, New Delhi SHRI HIRA LAL (Alternate )

SHRI B. GHOSH Automotive Research Association of India Ltd, Pune SHRI S. S. SANDHU (Alternate )

SHRI T. M. BALARAMAN Ltd, Pune SHRI V. M. MANEL ( Altertmtc )

SHRI V. M. MUNDADA Bajaj Tempo Ltd, Pune SHRI R. ,M. KANITKAR( Alternate )

SHRI S. R. TAPADE Central Institute~of Road Transport, Pune SHRI P. C. BARJATIA(Alternate )

SHRI R. S. DASS Central Farm Machine Training and Testing Institute, Budni SHRI M. L. MEHTA ( Alternow )

SHRI P K. SAHA Controllerate of Quality Assurance (Vehicles) [ DGAQ (V) 1, Ministry of Defence, Ahmednagar MAJORBALWINDER SINCH ( Alternate )

SHRI DINESH TYAGI Daewoo Motors India Ltd, New Delhi SHRI SURYA PATNAIK(Alternate ) SHRI N. K. KAUSHAL Directorate General of Supplies & Disposals, New Delhi SHRI S. K. GAUTAM(Alternate ) SHRI S. K. BHARIJ Department of Industrial Development, New Delhi SHRI R. K. TRIPATI(Alternate )

SHRI VEENU MATHUR Royal Entield Motors Ltd, Chennai SHRI N. RANGANATHAN(Alternate )

SHRI K. C. JAIN Escorts Yamaha Motors Ltd. Fatidabad SHRI R. K. GWTA (Alternate )

SHRI S.-B. GUPTA Hero Honda Motors Ltd, New Delhi SHRI HARJITSINGH ( Alternate )

SHRI U. K. KINI Ltd, Hooghly SHRI M. G. JHINGRAN(Alternate )

DR K. K. GANDHI Indian Institute of Petroleum, Dehra Dun DR MUKESHSAXENA (Alternate )

SHRI P V. -BHANDARE Kinetic Engineering Ltd, Pune

SHRI S. K. MUKHERJEE Mahindra 8c Mahindra Ltd, Nashik SHRI 2. A. MUJAWAR(Alternate )

SHRI I. V. RAO Maruti Udyog Ltd. Gurgaon ~HRI P. PANDA (Alternate )

( Continrred on page-6 ) 5 IS 14785: 2000

( Conlinuedfrom page 5 )

Members Representing

SHRI S. N. SRINIVASAN Automobiles Ltd, Mumbai SHRI K. D. DIGHE(Alternate )

DR A. N. OGALE Standing Committee ( Tech & Stores ) GIRT, Pune SHRI P UOAY KUMAR(Alternate )

SHRI LAKHINDERSINGH Swaraj Mazda Ltd, Chandigarh SHRI S. R. AGRAHARI(Alternate )

SHHI A. T. PHATAK Tata Engg & Loco Co Ltd, Pune SHRI A. V. KULKARN~(Alternate )

SHRI R. C. S~HI Vehicle Research & Development EstabIishment, Ahmednagar SHRI N. KARUPPAIAH(Alternote )

SHRI M. K. M~SHRA Vehicle Factory, Jabalpur (Ministry of Defence), OFB SHRI R. G. KAREMORE(Alternate )

SHRI F? N. RANGAN Volvo India Pvt Ltd, Bangalore SHRI PAULRAJEDWIN ( Alternate )

SHRI K. E. TAKAVALE Toyota Kirloskar Motors Pvt Ltd, Bangalore SHRIYOGAPRASAD ( Alternale )

SHRI A. R. GULATI Director General, BIS ( Ex-officio Member) Director ( Transport Engg )

Member-Secretary

SHRIA. K. NAGPAL Additional Director ( Transport Engg ), BIS

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Thus Indian Standard has been developed from Dot : No TED 8 ( 269 )

Amendments-Issued Since Publication

Amend No. Date of Issue Text Affected

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